1. Field of the Invention
The invention relates in general to the field of data networking and communications, and in particular to interconnecting computers to a local area network (xe2x80x9cLANxe2x80x9d) or a wide area network (xe2x80x9cWANxe2x80x9d) through data lines that carry power, network data and telephone data.
2. Description of Related Art
Packet networks (e.g. Ethernet) are used to connect computer systems. Various techniques exist for attaching devices to a computer network. Generally, attached devices are computer systems, but more recently other devices, such as telephones, are being attached to the computer network. Conventional telephones are analog devices designed to connect to circuit switched networks. The attachment of telephones to packet networks, and more particularly to local area networks (e.g. Ethernet) is a more recent phenomenon.
Network devices, such as networked personal computers, typically communicate via wired data lines and receive power from a separate line. For example, personal computers (xe2x80x9cPCsxe2x80x9d) may communicate Ethernet signals via category three (CAT-3) or category five (CAT-5) twisted pair wire and receive power from a second cable connected to a power source, such as a wall socket or a battery. However, it is desirable to be able to eliminate the need for the second cable.
Plain old telephone service (xe2x80x9cPOTSxe2x80x9d) combines a voice signal with a power signal. The combined signal is transmitted over twisted pair cable between the telephone and the line card at the public telephone exchange office. The line card also supplies power over the two wires carrying the voice signal. However, the voice signal supported by POTS is not sufficient for bandwidth intensive communications needs, such as, Ethernet communications. Similarly, ISDN communications transmit power and digital data over between an ISDN modem and a telephone switch. However, ISDN data rates are more than an order of magnitude lower than Ethernet data rates.
Additionally, telephone systems using private bridge exchanges (PBXs) typically have a wired connection that is separate from the network devices. This additional wired connection carries both telephone data signals and power to the telephone. The telephone data signals may be either digital or analog data signals that carry the voice conversations to and from the PBX to a telephone. The PBX is responsible for relaying the voice conversation to and from other users or out into the public telephone exchange. The PBX also supplies the telephone with power. In the event of a power outage, the PBX may have a back up power supply to allow users to continue to use their phones during the power outage.
POTS does have one important feature which is supported by some PBX systems. During a power failure, the telephone continues to operate. This is because power is supplied to the telephone directly from a backup power system at the PBX or the central office switch. This is a desirable feature of telephone systems.
In previous systems where a user has both a network device and a telephone, the user will have a cable connected to the network for network communications with the network device, a cable connected to a power source for the powering the network device, and a cable connected to the PBX for powering and carrying communications to and from the telephone. One problem with such a system is the cost of installing and maintaining all of these cables. Therefore, it is desirable to have a system that supplies the same general network device and telephone functionality to the user, but reduces the significant cabling costs of the system.
Conventional telephone signals are analog and continuous. One approach to attaching these devices to packet switched networks is to incorporate circuitry enabling telephones to attach directly to a packet network. An unsatisfactory issue related to this problem is that the packet attached telephone requires duplicate wiringxe2x80x94even though both computers and telephones attach to the same packet networkxe2x80x94because two physical connections are needed, one for the telephone and one for the computer. The duplicate wiring adds significant cost to the overall network installation. Therefore, what is needed is an apparatus that allows a telephone and computer to utilize the same wiring simultaneously.
Therefore, what is needed is a solution that reduces the wiring requirements to transmit data and power to a network device and a telephone without significantly reducing the functionality of the network device and the telephone.
The present invention provides an adaptor which supports supplying both telephone signals and data signals over a local area network medium such as a twisted pair wire for Ethernet. The adaptor according to one aspect of the invention comprises a first packet port, second packet port and a telephone port. Core logic is coupled to the first and second packet ports and to the telephone port and retransmits network packets which are received on the first and second packet ports and on the telephone port to at least one other of the first arid second packet ports and the telephone port. Data processing resources are coupled to the telephone port and to the core logic which translate network packets destined to the telephone port into telephone signals and to translate telephone signals destined to the core logic into network packets. This way, telephone data transmitted as network packets through a network are appropriately routed to the telephone and translated into standard telephone signals. Network packets which are destined to a network attached device other than the telephone are routed through the core logic according to standard network protocols.
The core logic according to alternative embodiments comprises a physical layer repeater, a datalink layer switch, or a higher layer router technology. Other data multiplexing techniques can also be utilized in the adaptor core logic.
The data processing resources which are coupled to the telephone port in some embodiments of the present invention comprise a medium access control unit for receiving network packets from the core logic, and for transmitting network packets to the core logic. Processing resources are coupled with the medium access control unit and perform analog-to-digital and digital-to-analog processing of telephone signals. Additional processing resources construct network packets according to higher layers of the protocol.
According to other aspects of the invention, the adaptor is included within a host computer. The first packet port on the adaptor is coupled to the host computer, either through a MAC unit coupled to the port, in the case that the core logic comprises a repeater or a switch, or through host bus interface logic, in case in which the core logic comprises a multiplexer for data from the network packets. The second packet port according to this aspect of the invention comprises a port to a local area network medium which is coupled to a network hub or other network logic at which packets carrying data from the first packet port and packets carrying digitized telephone signals from the telephone port can be combined onto the medium. The second packet port may comprise a repeater port or a full MAC unit depending on the particular implementation desired.
According to another embodiment of the invention, the adaptor is incorporated in a telephone. The telephone port is coupled to the telephone while the first and second packet ports are standard network connections. The first packet port is adapted for connection to a host computer while the second packet port is adapted for connection to the local area network medium which is coupled to the broader network.
One embodiment of the invention also includes an apparatus for providing electric power and telephone signals to the adaptor and the telephone across a transmission line across which the adaptor is coupled to a network device. A power and data coupler (xe2x80x9cthe couplerxe2x80x9d) is coupled to the transmission line, for example, at the network device. The transmission line is also adapted for transmission of a data signal. The data signal includes packetized telephone signal data for communications with the telephone. The coupler has a data input and a power input. Power from the power input is coupled with the data signal from the data input and the combined power supply current and data signal is coupled to the transmission line. The opposite end of the transmission line at the adaptor is coupled to a power and data decoupler (xe2x80x9cthe decouplerxe2x80x9d). The decoupler has a power output and a data output. Both the data output and power output of the decoupler are coupled to the adaptor. The combined power and data signal is decoupled by the decoupler, and the data signal is supplied to the data output and to the adaptor core logic and the power is supplied to the power output. The telephone port on the adaptor receives the power from the power output and receives the telephone signal data from the adaptor core logic. The telephone port couples the power and the telephone signal data together on a transmission line to make a combined power and telephone signal, which can be used by the telephone.